Method of preparing acrolein and acrylic acid



United States Patent 3,331,871 METHOD OF PREPARING ACROLEW AND ACRYLICACID Charles E. Ziegler, Therwil, Basel-Land, Switzerland, and Jamal 5.Eden, Akron, Ohio, assignors to The B. F. Goodrich Company, New York,N.Y., a corporation of New York No Drawing. Filed Jan. 27, 1964, Ser.No. 340,543 8 Claims. (Cl. 260-533) This invention relates to a new anduseful catalyst and to a method for preparing acrolein and acrylic acidby passing a mixture of propylene and an oxygen containing gas over thecatalyst at an elevated temperature, and, more particularly, pertains toa catalyst comprising oxides of Ni, Mo, tellurium and rhenium, and to amethod for preparing acrolein and acrylic acid by passing a mixture ofat least stoichiometric proportions of an oxygen containing gas andpropylene over or through the catalyst at a temperature of from about300 to about 450 C.

Because of the ready availability of propylene as a petroleum derivedchemical, numerous attempts have been made to use it as an ingredientfor the preparation of useful oxidation products having three carbonatoms.

Nickel molybdate in admixture with TeO has been described as a catalystfor the preparation of acrolein and acrylic acid in Belgian Patent623,214, but the conversion of propylene per pass is 68% and the yieldof useful oxidation products based on the propylene converted is 25% foracrylic acid and 7.5% for acrolein. The efiiciency is only of the orderof 22.1% at a temperature of 367 C.

With the catalyst of this invention it is possible to obtain conversionsof propylene per pass ranging from about 68 to substantially 100% withefi'lciencies from 45.5 to as high as 81. It is therefore apparent thatthe process can be adusted to obtain sufiiciently high conversions ofpropylene and yields of acrolein and acrylic acid so as to avoid thenecessity of recycling propylene. The small quantities of propylene thatmay remain unreacted can be burned with the vent gases.

In the process small quantities of carbon monoxide, carbon dioxide,acetic acid and acetaldehyde are also formed.

THE REACTANTS The propylene can be a commercial grade or it can containsubstantial quantities up to 50% of propane or other saturated volatilealiphatic hydrocarbons. The saturated hydrocarbons will consume someoxygen during the reaction but do not interfere substantially with theoxidation of the propylene to acrolein and acrylic acid. The only effectof saturated hydrocarbons appears to be the competition for some of theoxygen. Thus, if propylene containing substantial amounts of saturatedhydrocarbons is used, the amount of oxygen should be adusted tocompensate for that used in oxidizing .the paraffins. Ethylene is alsooxidized in part, but its effect also seems to be utilization of part ofthe oxygen. A large proportion of the ethylene goes through the reactorintact. The butylenes are also oxidized, but these are convertedprimarily to carbon oxides, with only small amounts of unsaturatedaldehydes or acids having four carbon atoms.

The oxygen can be supplied as air, as commercially pure oxygen or asoxygen enriched air. The ratio of oxygen should be at leaststoichiometric, i.e. at least 1 /2 mols per mol of propylene andpreferably from 33 to 100% excess based on the stoichiometric ratio.Ratios of oxygen less than stoichiometric will also convert some of thepropylene to acrolein and acrylic acids, but generally the percentage ofpropylene converted is fairly low and the yields of desired product islower than when an excess of oxygen is used. Any blend of oxygen and aninert gas can be employed as the oxidizing ingredient.

3,331,871 Patented July 18, 1967 It is desirable, but not essential, touse water vapor along with the propylene and oxygen. The role of wateris not clearly known. With no water vapor, usually conversion ofpropylene and yields of desired products are somewhat lower than thatwhen the reaction is run in the presence of steam. The amount of watervapor is not critical and from about 2 to about 6 mols per mol ofpropylene can be used. The most preferable range of water is from about2.5 to 4.5 mols per mol of propylene. Of course, if water presents aproblem in the separation steps after the reaction is completed, thennone need be used, but a slight sacrifice in yield usually results.

REACTION CONDITIONS The temperature should be between 300 and 450 C.,and preferably between 350 and 425 C. Below 300 C. the oxidation ofpropylene is too slow to be practical. Above 450 C. there appears to bea considerable amount of oxidation of both acrolein and acrylic acid,and such oxidation can be observed to occur at a slow rate as low as 450C. in the presence of the catalyst.

The reaction or contact time can vary from about 5 to about 40 seconds.For practical reasons a reaction time of from 7 to about 30 seconds ispreferred.

The reaction can be run in either fixed or fluid bed systems. Because ofthe advantages of easier temperature control with a fluid bed system, itis preferred. The oxidation is quite exothermic and development of hotspots in a fixed bed system is possible unless careful attention isgiven to .the control of the temperature.

CATALYST AND PREPARATION The catalyst comprises either (1) a mixture ofoxides of Ni, Mo, Te, and HReO or Re O or (2) NiMoO containing TeO ornickel tellurite and HReO, or Re O or (3) a mixture of NiMoO M00 TeO andHReO or R6207.

Mols M00 or its equivalent 800 NiO or its equivalent 160-800 TeO 25-375HReO or its equivalent as Re O 1-6 The nickel and molybdenum can bepresent either as oxides or as nickel molybdate or as a mixture ofnickel molybdate and nickel oxide. The preferred range of ingredients is800 mols of molybdenum oxide, 670-750 nickel oxide or salt, 50-200 TeOor other tellurite and l-2 of rhenium oxide.

For preparing a catalyst of the type defined under (1) above it isnecessary merely to blend thoroughly the ingredients of the mixture.

For preparing a catalyst of the type defined under (2) above a typicalprocedure is to dissolve 101.79 g. of Ni(NO -6H O in 100 ml. water byheating to about 50 C., dissolve 74.17 g. of ammonium molybddate in 100ml. water at about 50 C. Add the ammonium molybdate solution to thenickel nitrate. Dissolve 4.2 g. of .tellurium oxide in 8 ml.concentrated I-ICl, and add to the mixture. Thereafter add sufiicientconcentrated dropwise until neutral. Add an aqueous solution ofperrhenic acid or ammonium perrhenate. Mix well and evaporate to drynessin hot air at -90 C. Bake the dried catalyst at 400 C. for about 16hours. The rhenium compounds can also be added as perrhenic acid,ammoniurn perrhenate or R6207 to a paste of the remaining ingredientsprior to drying. After baking the catalyst is crushed and sieved. Meshsizes 10-18 (U.S. Sieve) are used for fixed bed systems and 80-325 meshfor fluid bed processes.

of nickel (i.e. catalyst containing a mixture of nickel.

molybdate and M less than equivalent amounts of nickel salts should beused.

For preparing supported catalysts on colloidal silica, the silica can beadded to the aqueous catalyst mixture or vice versa, prior to drying.Thereafter, the catalyst is treated as above.

If the support is a porous microspheroidal material, such asmicrospheroidal silica gelhaving a surface area of about 325 m. per g.it is preferable to first treat the silica-with concentrated NH OH,filter until fairly dry, then suspend the silica in water and add thesolution of ammonium molybdate and nickel nitrate, tellurium and rheniumcompound in increments prior to neutralization, while drawing a vacuumon the mixture of ingredients to attempt to fill all the interstices ofthe silica gel with the catalyst. After completing the blending of allthe materials, the supported catalyst is dried, baked, crushed andsieved.

Alternately, the catalyst can be prepared by first making a paste withthe molybdate and nickel ingredients and then thoroughly mixing in theTeO and the HReO The examples which follow are intended only as detailedexplanations of the invention and not as limitations.

Example I The catalyst used in this test had a molar ratio of 670 Ni,800 M00 50 TeO and 1 Re. It was prepared by dissolving, separately, therequired amount of ammonium molybdate and nickelous nitrate in water at50 C. and then adding the ammonium molybdate solution to the nickelousnitrate solution. A solution of the required amount of ,telluriurn oxidein a small amount of concentrated HCl is added at 50 C. to the solutionof nickel and molybdenum salts. At this stage the aqueous solutioncontains no precipitate. The mixture is now neutralized withconcentrated NH OH to form a precipitate. The requisite amount ofammonium perrhenate is added. The mixture is thoroughly mixed, dried andbaked at 400 C. for 16 hours. The finished catalyst was crushed andscreened to 8-18 mesh sieve (U.S. screen designation) for fixed bed runsand 80-325 mesh sieve for fluid bed runs.

Approximately 60 ml. of the catalyst were placed in a fixed bed reactorwhich consisted of a high silica glass tube about 28 cm. long, and 22mm. outer diameter. It was wound with three sets of electrical heatingelements, one of which extended along the entire length of the reactionsection and each of the other two extended about one-half the length ofthe reactor. The reactor contained an inlet forpropylene, one for anoxygen containing gas and one for steam. The reactor also contained athermocouple well, so that the temperature in the reaction area could bedetermined. The gaseous effluents from the reactor were passed through adrying tube and then a vapor phase chromatograph for continuous analysisof the products of the reaction.

The feed gases were preheated to a temperature of about 120200 C. beforeentering the reactor. The feed consisted of sufiicient air to provide 2/2 mols of oxygen per mol of propylene and 4 mols of steam per mol ofpropylene. The cold contact time was calculated at 18 seconds.

At a temperature of 390 C., 83.3% of the propylene was converted withyields of 37% acrolein and 39.7% acrylic acid. The respectiveefficiencies were 30.8% and 33.1%. At.400 C., 87.6% of the propylene wasconverted giving a yield of 26.8% acrolein and 49.7% acrylic acid.

The respective efficiencies were 23.5% and 43.5%

Another catalyst with a molar ratio of 800 Ni, 800 M00 50 Te. and 1 Rewas used with the same reactant ratios and contact time as describedabove. At 380 C. the propylene conversion was 78.9%, the acrolein yieldwas 69.9% and acrylic acid yield was 18.1%. At 405 C.

88.8% of the propylene was converted with yields of 54.1% acrolein and25.5% of acrylic acid.

, Example 11 A catalyst base was prepared by dissolving 176.6 g. of

(NH4)6MO7O244H2O in 400 ml. water, dissolving 191.93 I g. of Ni(-NO and89.37 g. of NiSO -6H' O in 400 ml.

water, adding the nickel salt solution to the molybdate solution andneutralizing with ammonia. The precipitate was then filtered and washedby resuspension in water until there was only a faint green color in thewash water.

The reactant ratios were the same as in the, previous ex-.

ample, contact time was 18 seconds.

With the catalyst having a Ni, Mo, Te, Re ratioof 400, 400, 25, 1 at 355C., 77.93% of propylene was converted to yield 63.4% acrolein and 25.7%acrylic acid. This same catalyst at 375 C. converted 93.1% of thepropylene, to yield 54.5% acrolein and 31.9% acrylic acid.

The catalyst with a ratio of 500 Ni, 500'Mo, 25 Te and 1 Re when usedwith the same reactant ratios and reaction conditions as above but at atemperature of 360 C. converted 89.5% of the propylene with yields of36.2% acrolein and 41.9% of acrylic acid. At 370 C. the propyleneconversion was 94.3% with a 24.5% yield of acrolein and 47.65% yield ofacrylic acid.

With a catalyst having a ratio of 660 Ni, 660 Mo, Te. and 1 Re, at 340C. and the remaining conditions and reactant ratios as above, 72.9%propylene conversion is obtained with 34.1% yield of acrolein and 24.4%yield of acrylic acid.

At Ni 800,.Mo 800, Te 40 and Re 1 ratios. at 330 C. with the remainingreaction conditions and reactant ratios as above about 50% of propyleneis converted with yields of 33.8%acrolein and 22.5% of acrylic acid.

This example shows that small amounts of rhenium will cause the reactionto proceed at considerably lower temperatures with good conversions ofpropylene and good yields of acrolein and acrylic acid.

The following example shows results obtained in a fluid bed reactor withan unsupported catalyst.

The reactor was a high silica glass tube having an inner area of 9.08cm. and a length of 5 ft. The reactor was heated externally by use of anelectrical heating element. Means were provided for preheating thereactants, A sintered glass plate was placed in the bottom of thereactor to keep the catalyst from entering the reactant inlets. In theseruns the catalyst was fluidized with hot air or a mixture of hot air andsteam. The reactor temperature was adjusted to 30-50. C. below thatdesired for oxidation of the propylene. Thereafter, propylene was fed.into the reactor and the reaction was allowed to proceed at the 1 ondsand the temperature was 325 C. The catalyst had a molar, ratio of 660NiO. 800 M00 50, TeO and 1 HReO It 'was prepared by theprocedure'described in Example 1.

Under these reaction conditions 89% of the propylene was converted, witha 13.9% yield ofacrolein and a 36.1%

yield of acrylic acid. The respective efficiencies were 12.4

and-32.1%.

It is apparent to those skilled in the art that numerous variations withrespect to .the catalyst composition, the ratio of reactants andreaction conditions are possible without departing from the spirit andscope of the invention as defined in the claims.

We claim:

1. A method of preparing a mixture of acrolein and acrylic acid,comprising passing a mixture of propylene and an oxygen containing gasin a molar ratio of from about 1.5 to about 3 mols of oxygen per mol ofpropylene and up to 6 mols of water vapor per mol of propylene through acatalyst bed at a temperature of from about 300 to about 450 C. with acontact time of from about 5 to about 40 seconds, the said catalystconsisting essentially of in a molar ratio 800 Mo, 160-800 Ni, 25-375TeO and 16 Re calculated as oxides.

2. The method of claim 1 in which the molar ratio of the catalyst is 670Ni, 800 Mo, 50 Te and 1 Re, calculated as oxides.

3. The method of claim 1 wherein the temperature is 350400 C.

4. The method of claim 1 in which the catalyst is in a fixed bed.

5. The method of claim 1 in which the catalyst is fluidized.

6. A method of preparing a mixture of acrolein and acrylic acid,comprising passing a mixture consisting of about 2.5 mols of oxygen and4 mols of water vapor per mol of propylene through a fluidized catalystbed at a temperature of about 375 C. and a cold contact time of about 18seconds, the catalyst consisting essentially of on a molar ratio, 400Ni, 400 Mo, Te and 1 Re calculated as oxides.

7. The method of claim 6 in which the catalyst consisting essentially ofon a molar ratio, 500 Ni, 500 Mo, 25 Te and 1 Re, calculated as oxides.

8. The method of claim 6 in which the temperature is about 400 C. andthe catalyst on a molar ratio, consisting essentially of 67 0 Ni, 800Mo, Te and 1 Re, calculated as oxides.

References Cited UNITED STATES PATENTS 12/1953 Middleton 260604 6/ 1965Fetterly et -al. 260533

1. A METHOD OF PREPARING A MIXTURE OF ACROLEIN AND ACRYLIC ACID,COMPRISING PASSING A MIXTURE OF PROPYLENE AND AN OXYGEN CONTAINING GASIN A MOLAR RATION OF FROM ABOUT 1.5 TO ABOUT 3 MOLS OF OXYGEN PER MOL OFPROPYLENE AND UP TO 6 MOLS OF WATER VAPER PER MOL OF PROPYLENE THROUGH ACATALYST BED AT A TEMPERATURE OF FROM ABOUT 300 TO ABOUT 450* C. WITH ACONTACT TIME OF FROM ABOUT 5 TO ABOUT 40 SECONDS, THE SAID CATALYSTCONSISTING ESSENTIALLY OF IN A MOLAR RATIO 800 MO, 160-800 NI, 25-375TEO2 AND 1-6 RE CALCULATED AS OXIDES.